Collusion means a secret agreement for some tricky, underhanded, or fraudulent purpose: "Drivers acted in collusion with warehousemen to rob the manufacturer." Collusion is close in meaning to conspiracy and should not be confused with collaboration. Connivance, from a Latin word meaning "to wink at," signifies avoidance of noticing something, assisting wrongdoing by not acting or speaking: "The connivance of museum guards circumvented regulations forbidding smoking." When one acts in collusion, he does something; when he connives, he ignores or overlooks something.
Dictionary of problem words and expressions. Harry Shaw. 1975.